Phlomis brachydon Essential Oil Against Bacterial Biofilm

Bacteria in biofilms show high resistance to antimicrobial and they cause many persistent and chronic bacterial infections. The failure of antibiotics in eradicating biofilm drives the need for novel approaches to effectively kill bacterial biofilms. Plant essential oils have been used for hundreds of years in traditional medicine to treat infections due to bacteria, fungi, and virus. The aim of the present study is to determine the effects of essential oil of Phlomis grown in north Jordan on biofilm-forming bacteria. Six bacterial clinical isolates were used in this study. The Minimum Inhibitory Concentration (MIC) and Biofilm Inhibitory Concentration (BIC) assays were performed in microtitre plates using a twofold dilution series. Phlomis essential oil MIC for planktonic bacteria ranged between 0.125 and 2 mg/mL. The most susceptible strains were MRSA and S. epidermidis. For bacteria grown in biofilm, the BIC ranged between 0.25 and 4 mg/mL. The most sensitive to Phlomis essential oil was S. epidermidis while the most resistant were P. aeruginosa and E. coli. Phlomis essential oil was able to inhibit initial adherence in the most tolerant isolate (E. coli) at sub-inhibitory concentrations. Phlomis essential oil showed a significant activity against all isolates in both planktonic and biofilm growth. It was able to inhibit initial adherence in the most tolerant isolate at sub-inhibitory concentrations.